Bring out the worst Craigslisting techniques you can find. Not a car, but putting your nicely finished instrument on asphalt is a surefire way to make everyone know you took great care of the item you'd like to part ways with...

A surefire way for me to tell you don't really care about the car you're selling on CL includes things like mentions of all the money you "invested" in your car. Just tells me it's a heap that keeps breaking down, or you are chasing a problem by throwing AutoZone parts at it.